The present invention relates to a string trimmer and in particular to a mechanism for shielding plants from the cutting path swept out by the rotating cutting line of the string trimmer.
String trimmers are portable hand-held outdoor gardening power tools, used for domestic and commercial grass cutting and are powered by electrical motors or small combustion engines. A string trimmer has a cutting head from which extends a cutting line, the cutting line commonly being a flexible plastic wire. The cutting line extends radially from the axis of rotation of the cutting head when it is rotatably driven by a motor. In the usual cutting mode, the cutting head and cutting line rotate a high rotational speed about an approximately vertical axis. The rotating cutting line is placed in close proximity to the grass to be cut. The grass caught within the path swept out by the rotating cutting line is severed when impacted by the cutting line.
This method of cutting grass is quick and highly effective and can be employed in dense grass or on a household lawn.
Indiscriminate cutting of soft vegetation may not be a problem when cutting in certain locations. However, the string trimmer may be used in a location where there is a mixture of soft vegetation where some parts need to be cut and other parts need to be left. One example is where the verge of a lawn abuts a flower bed containing small and delicate flowers which overhang the grass. In this example a string trimmer cannot be used easily to cut the grass without damaging overhanging flowers that are also caught in the path swept out by the rotating cutting line.
The example cited above illustrates a situation when the user wishes to protect certain plants from the rotating cutting line. There are, however, instances when the user wishes to protect the rotating cutting line from coming into contact with hard objects that the cutting line was not intended to cut, such as rocks or stones. When the rotating cutting line makes contact with such objects, it is liable to be damaged and therefore would need to be replaced. This situation is also undesirable and a device which protects certain plants from the rotating cutting line should also be capable of protecting the rotating cutting line from damaging itself against hard objects.
Prior art document EP 0 893 050 discloses a length of rigid metal wire attached to and extending outwardly from the motor housing of a string trimmer and is adapted to form a guard surrounding part of the path swept out by the rotating cutting line. EP 0 893 050 further discloses that the wire can also act as an edging guide. When acting as an edging guide, the rotating cutting line can cut a uniform edge along a lawn edge or a curb without coming into contact with the lawn edge or curb.
However, there are two problems associated with the guard disclosed in EP 0 893 050. The metal wire, when acting as a guard, does not surround the path swept out by the rotating cutting line. This leaves ample space for vegetation, such as overhanging plants or flowers, to enter into the path swept out by the rotating cutting line which results in damage to this vegetation.
Secondly, when the string trimmer is used in edging mode, the metal wire acts as a guide and therefore is unable to act as a guard. As such no protection is provided against cutting vegetation which is not intended to be cut.
Accordingly, there is provided a string trimmer comprising:
an elongate shaft; and
a cutting head rotatably mounted on one end of the shaft; a cutting member which extends from the cutting head;
an attachment mounted on the string trimmer; the attachment being pivotally mounted on the string trimmer by at least one pivot mechanism wherein the pivot mechanism comprises a latching mechanism about which the attachment is capable of latchably rotating relative to the string trimmer.
Preferably the attachment is a barrier which is capable of being used by an operator to move vegetation away from a path swept out by the cutting member.
The string trimmer according to the present invention has the advantage that the lightweight barrier which acts as a plant protector can be rotatably moved between a plurality of latchable positions without the need of dismantling any part of the string trimmer. When in use, a primary function of the barrier is to provide a barrier between overhanging plants and the path swept out by the rotating cutting line, while still allowing low level vegetation like for example grass, to pass below the lower edge of the plant protector and into the path of the rotating cutting line. The plant protector has two xe2x80x98in-usexe2x80x99 positions; one position for flat cutting and, the other for vertical edge trimming, such that when located in both xe2x80x98in-usexe2x80x99 positions the lower edge of the plant protector is approximately horizontal when the string trimmer is used in the appropriate way. The plant protector can be pivoted between these two positions and latch in them using the latch mechanism according to present invention.
The user may wish to maximize the cutting potential of the string trimmer by locating the plant protector the xe2x80x98out-of-usexe2x80x99 position thereby cutting all plants falling within the field of action not embraced by the protection cover regardless of their height. Again this can be achieved by pivoting the barrier to and latchably holding it in the xe2x80x9cout of usexe2x80x9d position.
The latching mechanism may comprise a first member having a wall, the wall comprising at least one flat and at least one trough; a second member held in rotational contact with the first member having at least on resilient tongue; the resilient tongue having a protrusion which is engaged with and capable of sliding along the wall as the first member rotates in relation to the second member so that it is either in contact with the trough or the flat, the tongue resiliently deforming as it slides along the wall depending on its position in relation to the wall; wherein as the barrier rotates relative to the string trimmer, the first member rotates in relation to the second member causing the protrusion to slide onto the wall, the latching mechanism latching the attachment in the predetermined position when the protrusion engages with the trough.
The flat may be straight or may be curved along its length. Alternatively, the flat may undulate along its length.
The wall may be formed around the hexagonal collar, the sides of the hexagonal collar forming the flats, the troughs being formed between adjacent flats.
When the wall is formed around a hexagonal collar, the flats are straight along their length. Such a collar is described in the first embodiment of the present invention.
Alternatively, the wall may be formed around a circular collar, troughs being spaced around the periphery of the circular collar, the parts of the periphery of the circular collar between the troughs forming the flats.
When the wall is formed around a circular collar, the flats are curved along their length. Such a collar is described in the second embodiment of the present invention.